In the production of shaped articles from foam materials, the foam-forming substance is poured into a mold which must then be closed very quickly before the foam develops and swells out from the mold. Further, in order to avoid the formation of air pockets within the shaped foam articles, it is expedient that the mold to be filled by the foam is pivoted into inclined position such that after the filling an air outlet in the mold is in as high as possible a possible position. The mold is held in this inclined position until the foam material is cured.
Endless conveyor tracks are known on which mold carriages supporting the molds to be filled by the foam are adapted to travel around. At a filling station, an operator takes care of the pouring of the substance, of the closing of the mold and of the subsequent pivoting of the mold into the inclined position required for ventilation.
This manually operated system suffers from various drawbacks. On the one hand, the velocity of circulation of the mold carriages is limited due to the manual operations, and, on the other hand, problems arise from the fact that closing of the mold as well as the subsequent pivoting thereof must be effected within a minimim period of time (about 5 seconds) while the foam material is still in a liquid state, i.e. before this material has started to develop foam.
It is the object of the present invention to modify known systems of the above-indicated type by providing a mold assembly operating mechanism which acts in such a manner that the steps of closing the molds as well as the subsequent pivoting thereof are performed automatically within an extremely short period of time.
According to the present invention, this object is achieved by providing a pivoting cylinder which along with its piston rod is adapted to be moved into and out of engagement with said upper closing portion by means of a lifting cylinder, and which pivoting cylinder alone provides for the closing of all closing portions when its piston rod is extended, and for the subsequent pivoting of all closing portions when its piston rod is retracted. Said pivoting cylinder and said lifting cylinder are mounted on a movable support adapted to be moved to and fro along a predetermined portion of said conveyor track and to travel together with said mold carriages in the direction of conveyance as long as said piston rod of said pivoting cylinder is engaged with said closing portion. A self-locking interlock or automatic lock is provided between upper and lower closing portions in order to prevent opening of said closing portion during the pivoting thereof. Said closing portion further includes a latch level which, when the inclined position is reached, enters into a guide track provided along said predetermined portion of said conveyor track thereby to prevent said closing portion from swinging back into the horizontal position when said closing portion and said piston rod of said pivoting cylinder have been disengaged from each other. Movement of said piston rod of said pivoting cylinder is stopped when the desired inclination of said closing portion including the mold enclosed thereby is attained.
By an arrangement using only one pivoting cylinder, an extremely simple mold assembly operating apparatus is provided which, in cooperation with the self-locking interlock (automatic lock) between the upper closing portion and the lower closing portion (mold holders) in substantially one operation first closes the closing portion thereby to close the mold, and thereafter brings both parts into the desired inclined position. To this end the piston rod of the pivoting cylinder is engaged with the initially open upper closing portion, and a corresponding control means effective upon filling of the mold causes the piston rod of the pivoting cylinder to be extended until upper and lower closing portions are locked. The subsequent retract movement of the piston rod into the pivoting cylinder thereupon produces the torque which moves the closing portion into the inclined position. As the piston rod of the pivoting cylinder need be engaged with the upper closing portion but once, whereupon closing and pivoting of the closing portion is effected by a single extension and subsequent retraction of the piston rod, it becomes possible to effect these two motions not only automatically, but also within the required short period of time. The lock lever in combination with the guide track ensures that the closing portion, upon reaching the inclined position, is maintained in this position as the mold is thereafter advanced along the track until the foam material is cured. As the pivoting cylinder is no longer needed for maintaining the inclined position of the mold carriage once the guide track is engaged, it may be released from engagement with this closing portion and returned for operating the closing portion of the next mold carriage. In order to effect this disengagement in an easy manner, the retraction of the piston rod into the pivoting cylinder is interrupted as soon as the desired inclination of the closing portion has been reached, and the pivoting cylinder is then raised out of engagement with the closing portion by means of the lifting cylinder.
In an advantageous embodiment of the invention, it is contemplated that the pivoting cylinder and the lifting cylinder are adapted to travel to and fro across a predetermined path or distance of the conveyor track and to move in synchronism with the mold carriages in the direction of conveyance as long as the piston rod of the pivoting cylinder is engaged with a closing portion. As the pivoting cylinder moves along the endless conveyor track at the same velocity as the mold carriages while it closes and thereafter pivots the closing portion, the mold carriages are allowed to continuously travel around the endless conveyor track without having to be stopped at the filling, closing and pivoting station.
Another embodiment of the present invention is characterized in that said lower closing portion is mounted for rotation about a first horizontal axis on said mold carriage; said upper closing portion being connected to said lower closing portion for rotation about a second horizontal axis extending parallel to said first axis; said pivoting cylinder being mounted on a support for rotation about a third axis extending in parallel with said first and second parallel axes; and said lifting cylinder being mounted to said support with said piston rod of said lifting cylinder being affixed to said pivoting cylinder.
In an advantageous further embodiment of the present invention, the front face of each upper closing portion has provided thereon a pair of first levers, one at each side, opposing said pivoting cylinder, which levers are interconnected by means of a rod, a pipe or the like. The head of said piston rod of said pivoting cylinder is formed with a U-shaped configuration so as to be adapted to engage said rod or the like.
Additionally, a further advantageous embodiment is characterized in that both end faces of each upper closing portion have pair of bell cranks, one being pivotally mounted at each side of the mold carrier, opposing said pivoting cylinder, whereby said first lever and said bellcrank are coupled with each other by means of a guide bar. A latch lever is being pivotally mounted at the side of said upper closing portion opposite from said pivoting cylinder said latch lever being connected to said bellcranks by means of a connecting rod which is pivotally mounted at both ends thereof and the lengths of which is variable.
According to the present invention, the automatic lock is provided in a simple manner in that a pawl is pivoted near the end of each guide bar remote from the pivoting cylinder, which pawl cooperates with a stop point or detent in order to prevent the lock from being released.
Preferably, the angle of inclination of the mold holder is adjustable to 60.degree., which adjustment is effected in ready manner in that the lock lever is secured to the lower closing portion in such a way that its inclination relative to the lower closing portion is adjustable. However, any desired angle of inclination may be set.
In another advantageous embodiment of the present invention, movement of the piston rod of the pivoting cylinder upon reaching the desired inclination of the mold holder and the enclosed mold members is controlled by a limit switch adapted to be actuated by the lock lever.